Clinton said that agreeing to a permanent extension would be a mistake, however.

"The real issue is not whether they should be extended for another few months. The real issue is whether the price the Republican House will put on that extension is the permanent extension of the tax cuts, which I think is an error," Clinton said.

Those tax cuts, enacted in two waves in 2001 and 2003, are set to expire early next year — setting up a showdown between the Democrats and the Republicans, who differ over whether to extend them for upper earners. Democrats want them extended for everyone except the wealthy, while Republicans insist on across the board renewal.

Obama agreed to renew the tax cuts in 2010 in exchange for concessions from congressional Republicans — but has since made raising taxes on upper earners a major campaign theme. The issue will likely come to a head in either the lame duck session of Congress or during the new session of Congress in January.

" The fact that former President Clinton supports stopping all of the tax hikes scheduled for January 1 is very, very big news," Michael Steel, spokesman for House Speaker John Boehner, said.

"As you know, the Republicans are united on this issue and agree with the former President, and the House will have such a vote before the August recess. Will Senate Democrats follow suit? Will President Obama get off the campaign trail and lead on this issue, now that his predecessor has weighed in? Inquiring minds want to know," Steel said.